This invention relates to a closure device for a plastic container, and more particularly to a tamperproof closure.
Plastic containers for which this invention is intended are commonly used in the medical and health industries to store and transport liquids, drugs, pills and the like, both prescription and non-prescription. The containers are generally disposable and are made of thermoplastic material having a hermetically sealed top. The manufacture of such containers typically utilizes the blow-fill-seal technology whereby the container is molded, filled with the contents of choice, and sealed in a single operation. The blow-fill-seal method of producing such containers readily lends itself to mass production, primarily because of its simplicity in manufacture and low cost.
One of the features of blow-fill-seal containers is that during the manufacturing process, the neck of the container can be constructed to have a frangible portion between the intended body and integral cap of the container. Closure devices are then used in conjunction with the containers and are constructed so that the operation of the closure device breaks the frangible portion, and opens the container.
Closure devices of the foregoing general type have taken many forms over the years. For example, Komendowski U.S. Pat. No. 3,804,282, relates to a closure device which employs a cap which must first be threaded downwards to break the frangible portion, and then unthreaded upward in counter-clockwise rotation in order to open the container. Rivli U.S. Pat. No. 4,096,962 relates to a separate chisel-containing ring opener for opening hermetically sealed containers such that as the ring opener is threaded downward onto the container, downward pressure seats the chisels into a ridge on the container. When the ring opener is unthreaded upwardly, the chisels break the frangible portion to open the container.
The opening action of rupturing a frangible portion of a sealed container has been demonstrated in a variety of forms. For example, in Bellamy, U.S. Pat. No. 4,111,325, an outer ring is used which, when rotated downwardly, produces an upwardly jacking action on an overcap, thereby breaking the frangible section. Another example is D'Amico U.S. Pat. No. 4,434,904 wherein jacking action is produced when the outer portion is rotated and jacking ring fingers push upwardly on the top of the closure.
Yet another example is illustrated in Bertaud U.S. Pat. No. 4,494,663, wherein a screw type cap member has a tear-away portion and internal threading which engages threading on the container. Upon removal of the tear-away portion, the cap engages the container threading and the container frangible section is broken when the cap is downwardly rotated. Subsequent unthreading of the cap opens the container.
Such devices are not entirely satisfactory because they involve complex jacking action, downward rotation, frangible sections on both outer and inner caps, their manufacture is complicated, and, despite their construction, are often difficult to open.